Carboxy-terminated copolymers of chloroprene and vinyl ferrocene

ABSTRACT

Copolymers of chloroprene and vinyl ferrocene (VF) are disclosed along with preparative procedures therefor. The copolymers are produced in an organic solvent when polymerization is initiated by a carboxy-containing azo compound, such as, 4,4&#39;&#39;-azobis(4cyanovaleric acid), thereby forming a copolymer of chloroprene and vinyl ferrocene. The copolymers are useful in propellant formulations as a binder where high burning rates are desired.

United States Patent Reed, Jr. May 27, 1975 [54] gg g ggg g fggg OTHER PUBLICATIONS OF P N L Bamford et al., Trans. Faraday $06., 56, 932-942, FERROCENE 1960) [75] Inventor: Samuel F. Reed, Jr., Holland, Pa. Arimoto et al., J. Am. Chem. Soc, 77, 6295-6297,

(1955). [73] Assgnee' The Umted States Amema as Pittman, J. Polymer Science, Part, B, 6, 19-21 (1968).

represented by the Secretary of the B d t l I Ch Ab 67 N 824l2f 1967 Army, Washington, DC. 8 e a [22] Filed: Dec. 7, 1970 Primary Examiner-Benjamin R. Padgett Assistant ExaminerE. A. Miller [21] Appl' 95890 Attorney, Agent, or Firm-Robert P. Gibson; Nathan Edelberg; Jack W. Voigt [52] US. Cl. 260/439 CY; 260/82.1 [51] Int. Cl C08d 3/14 [57] ABSTRACT [58] Field of Search 260/439 CY, 82.] copolymers of chloroprene and vinyl fen-Ocene (VF) are disclosed along with preparative procedures there- [56] References cue! for. The copolymers are produced in an organic sol- UNITED STATES PATENTS vent when polymerization is initiated by a carboxy- 2,877,212 3/1959 Seligman 260/775 containing azo compound, ch o 3,518,241 6/1970 Durling 260/895 cyanovaleric acid), thereby forming a copolymer of 3,586,552 971 otts et a 1 9/20 X chloroprene and vinyl ferrocene. The copolymers are 3,718,633 2/l973 Baldwin et a1. 149/19 useful in propellant formulations as a binder where FOREIGN PATENTS OR APPLIcATIoNs hlgh burning rates are desired- 60l,243 7/1960 Canada 260/439 CY 1 Claim, N0 Drawings CARBOXY-TERMINATED COPOLYMERS OF CHLOROPRENE AND VINYL FERROCENE BACKGROUND OF THE INVENTION Considerable literature exists on the preparation of polydiene with carboxyderminal groups prepared by both anionic and free radical initiators.

The preparation of vinyl ferrocene may be accomplished by the method disclosed by F. S. Arimoto and A. C. Haven, .1. Am. Chem. Soc. 77, 6295 (1955).

Well known in the propellant field is the fact that the burning rate of many solid propellants can be increased by the introduction of certain iron-containing additives. Many ferrocene derivatives have been utilized as additives for this purpose, usually in the form of liquids which also serve as plasticizing agents. In the liquid state the ferrocenes display the inherent disadvantages characteristic of liquid additives, such as loss by evaporation, migration, etc., and consequently, the propellant systems suffer, particularly on long term storage.

Thus, a need exists for a modified form of ferrocene additive which form is not subject to being lost by evaporation or migration from a stored propellant composition.

An object of this invention is to combine the ferrocene additive with the binder being utilized in the propellant system.

Another object is to combine a ferrocene derivative and a binder material via a polymerization technique into a serviceable prepolymer which is produced in high yield and which is suitable for propellant mixing and curing.

A specific object of this invention is to copolymerize a binder material and a catalyst material to provide a liquid copolymer which is capable of undergoing a cure reaction when used in a propellant composition to form a rubber-like binder material having a burning rate catalyst agent as an integral part thereof.

SUMMARY OF THE INVENTION Vinyl ferrocene is copolymerized with chloroprene in an inert organic solvent after the polymerization reaction is initiated by a carboxy-containing azo compound, such as 4,4'-azobis(4-cyanovaleric acid). The liquid copolymer is characterized by its molecular weight which is in the range of from about 1000 to 10,000, its carboxy-end group content from about 0.5 weight percent to about 9 weight percent, and its iron content from about 0.5 weight percent to about weight percent. The liquid copolymer is capable of undergoing a cure to a final rubber-like state.

DESCRIPTION OF THE PREFERRED EMBODIMENT The copolymer formed by reaction of chloroprene with vinyl ferrocene is useful as a combination binder and burning rate catalyst for solid propellant compositions.

The liquid copolymer is characterized by its preferred molecular weight range from about 1000 to LII about 10,000, its preferred carboxy-end group content from about 0.5 weight percent to about 9 weight percent, and its iron content from about 0.5 weight percent to about 15 weight percent. The liquid copolymer of chloroprene and vinyl ferrocene is produced by a procedure as described by the descriptive technique set forth below as Example I. Table I below sets forth additional experimental data on preparation of chloroprene-VF copolymers. The ch1oroprene-VF mole ratios for preparations of Table 1 were varied from approximately 46:1 to 7:1 with copolymerizations taking place in dioxane. The initiator used for these prepara tions was 4,4'-azobis(4-cyanovaleric acid). Table ll below, sets forth the physical property data for chloroprene-VF copolymers produced with the concentrations set forth in Table I. The chloroprene-VF mole ratios may vary from approximately 100:1 to about 1:1. The ratio of 1:1 yields a copolymer with an iron content of about 15 weight percent. The organic solvents wherein copolymerizations are conducted may be toluene or dioxane, dioxane being preferred. Polymerization temperatures may conveniently be maintained in the range of 60-80C. Reaction times may vary over the range of 24-12O hours; however, a reaction time in the range of about 72 hours is preferred.

Copolymers having molecular weights ranging from about 1000 to about 10,000, carboxy-end group contents of from about 0.5 to about 9 weight percent of the copolymer, and an iron content from about 0.5 weight percent to about 15 weight percent of the copolymer are easily obtained by varying the reaction conditions and concentrations of reactants and initiators. Other representative carboxy-containing azo compounds such as 3,3'-azobis(3-cyanobutyric acid), and 2,2'-a2obis-(2-cyanopropionic acid) may be employed as initiators for the polymerizations of this invention.

EXAMPLE I PROCEDURE FOR POLYMERIZATION OF CHLOROPRENE AND VINYL FERROCENE To a glass high-pressure reactor (aerosol tube) are introduced 30 ml. of dioxane, 1.0g (0.00467 mole) VF, 19.0g (0.25 mole) chloroprene, and 2.03g (0.0066 mole) 4,4'azobis(4-cyanova1eric acid). The reactor is attached to a vacuum line and deaerated by three alternate freeze-thaw cycles. The reactor is then removed from the vacuum line and placed in an oil bath at 6667C. Heating is continued for a period of 72 hours. After cooling, the reactor is vented, the solvent removed by evaporation and the copolymer reprecipitated by dissolving in ether followed by the addition of methanol. After decanting the solvents, the copolymer is stripped of excess solvents on a rotatory evaporator and finally dried at 75C under reduced pressure (1 mm.Hg) for a period of 25 hours. The yield of copolymer is 20.0g percent), The liquid copolymer (methanol insolubles) is characterized by its molecular weight (3300), carboxy-end group content (1.29 weight percent) and elemental analysis (percent Fe1.3 percent).

3 TABLE u Physical Property Data for chloroprene-VF Copolymcrs Calculated ('O H eight '0 made on the basis of two C(). .H groups r h i f r the molecular weight values reportedv Calculated Fe content made on the basis of the ratio ol' eomonomcrs initially charged into the reactor.

The copolymers of this invention may be used as the binder-catalyst for a solid propellant composition. The copolymers may be used in the propellant composition in amounts from about 5 weight percent to about weight percent. The remaining propellant ingredients exclusive of processing aids (such as lecithin) and trace amounts of other additives (e.g., stabilizing, ballistic, special curative, and the like) may be comprised of a plasticizer such as isodecyl pelargonate, a metal fuel such as aluminum, and an inorganic oxidizer such as ammonium perchlorate.

An example of a propellant composition using the copolymers of this invention is set forth under Example 11 below.

EXAMPLE 11 Weight Ingredient Percent Chloroprene/Vinyl Ferrocene Copolymer Binder 10.0 lsodecyl pelargonate plasticizer 10.0 Aluminum powder 10.0 Ammonium perchlorate 70.0

4 formulations. Those skilled in the art will recognize that the other propellant ingredients may be varied to include metal additives (e.g.. aluminum powder or other powdered metals used in the art) in amounts from about 5 to about 20 weight percent. inorganic oxidizer such as, ammonium perchlorate, from about 10 to about 72 weight percent. Other plasticizers may he used with the copolymers of this invention. Among the important plasticizers are nonvolatile organic liquids or low melting solids, especially the phthalie, adipatc. and sebacate esters, and aryl phosphate esters. Plastieizer content is determined by the desirable properties required for a propellant formulation. Generally, plasticizer amounts from about 5 to about 30 weight percent is the range meeting most requirements. Special processing aids such as lecithin and trace amounts of additives known in the art for their specific contributions to the ballistic, castibility, and storage properties of the propellant may be added to the propellant formulation.

I claim:

1. The carboxy terminated-copolymers of chloroprene and vinyl ferrocene pprepared by the method comprising reacting vinyl ferrocene and chloroprene in the presence of a suitable polymerization initiator in an inert organic solvent at a reaction temperature and for a reaction time period sufficient for said reaction to take place after which solvent removal is effected and said copolymers are dried at a suitable drying temperature while under reduced pressure; said suitable polymerization initiator being 4,4'-azobis(4-cyanovaleric acid); said inert organic solvent being selected from dioxane and toluene; said reaction temperature being in the range of about 60C to about 80C; said reaction time being from about 24 hours to about 120 hours; said drying is accomplished at a suitable temperature in the range of about C to about C and said reduced pressure is in the range of about 1 millimeter; said reacting chloroprene and vinyl ferrocene in mole ratios from approximately :1 to 1:1 to form said copolymers characterized by a molecular weight in the range from about 1000 to about 10,000, carboxy-end group content of about 0.5 weight percent to about 9 weight percent, and an iron content of about 0.5 weight percent to about 15 weight percent. 

1. THE CARBOXY TERMINATED-COPOLYMERS OF CHLOROPRENE AND VINYL FERROCENE PREPARED BY THE METHOD COMPRISING REACTING VINYL FERROCENE AND CHLOROPRENE IN THE PRESENCE OF A SUITABLE POLYMERIZATION INITATOR IN AN INERT ORGANIC SOLVENT AT A REACTION TEMPERATURE AND FOR A REACTION TIME PERIOD SUFFICIENT FOR SAID REACTION TO TAKE PLACE AFTER WHICH SOLVENT REMOVAL IS EFFECTED AND SAID COPOLYMERS ARE DRIED AT A SUITABLE DRYING TEMPERATURE WHILE UNDER REDUCED PRESSURE; SAID SUITABLE DRYING MERIZATION INITATOR BEING 4,4''-AZOBIS(4-CYANOVALERIC ACID); SAID INERT ORGANIC SOLVENT BEING SELECTED FRIM DIOXANE AND TOLUENE; SAID REACTION TEMPERATURE BEING IN THE RANGE OF ABOUT 60*C TO ABOUT 80*C; SAID REACTION TIME BEING IN THE RANGE OF ABOU HOURS TO ABOUT 120 HOURS; SAID DRYING IS ACCOMPLISHED AT A SUITABLE TEMPERATURE IN THE RANGE OF ABOUT 70*C TO ABOUT 75*C AND SAID REDUCED PRESSURE IS IN THE RANGE OF ABOUT 1 MILLIMETER; SAID REACTINHG CHLOROPRENE AND VINYL FERROCENE IN MOLERATIOS FROM APPROXIMATELY 100:1 TO 1:1 TO FORM SAID COPOLYMERS CHARACTERIZED BY A MOLECULAR WEIGHT IN THE RANGE FROM ABOUT 1000 TO ABOUT 10,000, CARBOXY-END GROUP CONTENT OF ABOUT 0.5 WEIGHT PERCENT TO ABOUT 9 WEIGHT PERCENT, AND AN IRON CONTENT OF ABOUT 0.5 WEIGHT PERCENT TO ABOUT 15 WEIGHT PERCENT. 